Xerographic cascade developing apparatus



G. H. ROBINSON XEROGRAPHIC CASCADE DEVELOPING APPARATUS Filed April 3, 1963 GENE H. ROB/NEON INVENTOR ATTORNEYS United States Patent Ofilice 3,173,895 Patented Mien. 16, 1965 3,173,805 XERGGRAPHIC CASCADE DEVELOllNG APPARATUS Gene H. Robinson, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Apr. 3, 1963, Ser. No. 270,365 6 Claims. (Cl. 118637) This invention relates to electrography and in particular to a cascade developing apparatus.

In the process of electrography an electrostatic image is produced upon an insulating layer. For example, in Xerography a photoconductive insulating layer supported on a conductive backing is given a uniform electrostatic charge over its surface and then exposed to a light image to discharge the electrostatic charge in the areas of the layer which are exposed to light while leaving electrostatic charges in the dark areas. The electrostatic image may be developed by cascading a. finely divided material or powder over the plate. The resulting visible powder image may be fixed to the insulating layer or transferred and fixed to a sheet of transfer paper to produce a permanent copy. As is well known in the art, the developer may comprise a finely divided pigmented resin powder mixed with a granular carrier material. The composition of the mixture is usually such that the carrier particles impart to the powder particles electrostatic charges opposite in polarity to the charge on the electrostatic image which it is desired to develop.

One known type of cascade developing apparatus which is adapted for use with a continuous roll or sheet of electrographic material to be developed, requires complicated, bulky, and expensive bucket-type conveyor means for taking cascaded developer back to the point of origin. In a second known type of cascade developing apparatus, the electrographic sheet to be developed is fixed to the apparatus and the apparatus is either rocked back and forth or rotated. This second type of apparatus is not adapted to continuous machine operation, but is limited to use with a single sheet or plate of electrographic material.

According to the present invention a cascade developing apparatus is provided which does not require the complicated, bulky, and expensive conveyor means necessary in the first known type of device mentioned above and which does not have the restriction of being limited to the development of a single electrographic plate, which restriction is inherent in the second known type of device mentioned above. tion is well adapted for use with either a continuous roll or sheet of electrographic material or with a single plate of electrographic material. The preferred embodiment of the present invention comprises a housing for containing the developer material which housing is provided with an opening in its bottom wall, the edges of which are placed in contact with the electrographic sheet and define the area to be developed. The portion of the bottom wall of the housing defining the opening, and the sheet are preferably positioned at an angle of between 45 and 70 to the horizontal. A hopper is pivotably mounted within the housing by means of a leak-proof hearing at a point adjacent the upper edge of the opening. A crank arm connected to the housing and extending through said bearing is an example of suitable means for pivoting the hopper. The hopper is adapted to contain developer when it is located in the lower part of the housing, and is adapted to cascade developer across the area to be developed after it has been moved into the upper part of the housing. It is preferable to have the crank arm ex. tend through a leak-proof seal, especially when liquid developers are used. To return the cascaded developer The apparatus of the present invenback into the hopper, the housing is rotated about 90 to cause the developer to flow into another corner thereof, the hopper is then pivoted about 90 to return it to its lower position, and the housing is then rotated back to its original position which causes the developer particles to flow back into the hopper, whereby the apparatus is ready for a second developing operation. After one or more passes of the developer across an electrostatic image, the electrographic sheet may be removed and replaced with another one, or if the sheet is in the form of a continuous roll, the roll may be advanced to position a second electrostatic image beneath the opening in the housing. in one embodiment the housing and the hopper are manually operated, for example, the housing is held by hand. In another embodiment the housing is rotatably mounted on support means whereby the opening is always returned to the same area after the pivoting of the housing to eilect return of the developer material back into the hopper. The present invention is primarily for use with developers of the dry powder type, as described above. The liquid type, such as that disclosed in Metcalfe et al., US. 2,907,674, poses no great problem of conveyance. However, the present apparatus can be used with liquid developers, if desired.

It is therefore a principal object of the present invention to provide a compact, economical, and simple cascade developing apparatus for use with either a single electrographic sheet or with a continuous roll of electrographic material.

It is a further object or" the present invention to provide a cascade developing apparatus which may use either a liquid or a dry developer.

it is a still further object of the present invention to provide a simple, compact, and economical cascade developing apparatus for use with an electrographic material which may either remain stationary or move along a plane during development.

It is another object of the present invention to provide a cascade developing apparatus which is particularly suitable for use in micro-image work because it can be made small and compact and does not require movement of the electrographic sheet.

These and other objects of the present invention will be more fully understood from the following detailed description and attached drawings in which:

FIG. 1 is a perspective cross-sectional view through the preferred embodiment of the invention; and

FIGS. 2A through 2E inclusive are a series of sequential operational views showing the relation of the housing, the hopper, the developer, and the electrographic material to be developed during a cycle of operation.

PEG. 1 shows a preferred embodiment of the present invention in which the developing apparatus is in its preloading position. The developing apparatus comprises a rectangular housing 4 having an end wall 6 provided with an opening 8 for introducing the developer material into the housing 4. The opening 8 is closed by means of a cover plate 10 and screws 12. A hopper 14 is pivotably mounted within the housing 4 by means of a leak-proof bearing 16 in one or both of th side walls of the housing 4 and a crank arm 18 which projects from the hopper 14 through the bearing 16. The hopper 14 can rotate through about a 90 angle. The housing 4 is provided with a bottom wall 22 having an opening 24 under which the electrographic material 25 bearing an electrostatic image is positioned. Developer material is introduced into the hopper 14 through the opening 8. The opening 3 can be omitted and the developer material introduced into the hopper through the opening 24. When the hopper 14 is moved about 90 (as described below in connection with FIG. 2), the developer mate rial flows out of the hopper 14 across the opening 24 and into the corner 28 of the housing 4. The rear edge of the opening 24 is tapered to a sharp edge to provide for the flow of the developer material across the electrographic material 26 and into the corner 28 of the housing and to prevent any leakage of developer out of the housing 4. The edges of the opening 24 must form a fiat rectangle, but otherwise the contour of the various walls of the housing 4 is not critical. When (as described below with reference to FIG. 2) the housing 4 is rotated about 90, the developer material flows from the corner 28 of the housing 4 to the corner 32 of the housing 4.

The hopper 14 is shaped and positioned in the housing 4 such that the top of the wall 34 of the hopper 14 fits snugly against the wall 36 of the housing 4. The upper end of the wall 34 is tapered to a sharp edge to aid reentry of the developer material into the hopper 14. When the preferred embodiment of FIG. 1 is used with a liquid developer, a seal 38 is provided in the bottom wall 22 around the opening 24 and a seal 40 is provided in the wall 34 and the side walls of the hopper 14. Although the preferred embodiment of the present invention shown in FIG. 1 may be used with a single plate or sheet of electrographic material, it is shown in FIG. 1 for use with a continuous roll of electrographic material 26. The sheet of electrographic material 26 is supported by means of rollers 42 and 43. The roller 42, for example, may be mounted in a support 44 by means of a rod 46. The housing 4 is provided with a bearing 48 attached to the wall 36. The housing 4, by means of the bearing 48, is mounted for rotation on a support 59. Stop means may be provided in the bearing 48 or in the support 54) to limit rotation of the housing to rotation through about a 90 angle. The developing apparatus may be constructed of metal, such as stainless steel, or of plastic.

FIG. 2A shows the apparatus immediately prior to a development cycle. With the apparatus in this position, the cover plate 10 is removed and the hopper 14 is partly filled with a developer. The cover plate 10 is then replaced and the apparatus is ready for use. FIG. 2B shows the hopper 14 rotated about 90 in the direction indicated by the arrow 60 from its initial position. When the hopper 14 is in this position (28), the developer flows out of the hopper '14, across the opening 24 and into the lowerportion 28 of the housing 4. FIG. 2C shows the housing after rotation about 90 in the direction indicated by the arrow 62, whereby the developer flows from the lower portion 28 to the upper-end portion 32. FIG. 2D shows the hopper 14 rotated back about 90 in the direction indicated by the arrow 64 back into its original or initial position, the developer staying in the upper-end portion 32. FIG. 2B shows the housing rotated about 90 in the direction indicated by the arrow 66, whereby the developer flows from the upper-end portion 32 of the housing back into the hopper 14. The developing apparatus is now back in its initial position and is ready for another pass of developer across the electrographic material. The electrographic material 26 is shown in FIGS. 2A through 2E as a portion of a continuous roll of material. After one or more passes of the developer composition across an electrostatic image to be developed the electrographic material is advanced to position the next electrostatic image to be developed beneath the opening 24 of the developing apparatus.

The preferred embodiment of the present invention is easily adapted to automatic control, since the housing requires only a rotation from a first to a second position about a stationary pivot point and the hopper requires a rotation from a first to a second position and then back to the first position.

An example of the operation of the invention is as follows.

The developing apparatus was loaded with a developer consisting of 97% iron filings (120 mesh) and 3% elutriated toner (92% Piccolastic Record Resin manufactured by Penn. Resins, 3% carbonblack, 3% spirit soluble nigrosine, and 2% 10-501 black) which had been classified so that the maximum particle size was 5 A photoconductive layer bearing an electrostatic latent image (35 mm.) on its surface was placed at a 45 angle with the horizontal and a developing apparatus similar to that shown in FIG. 1 was placed so that the opening 24 in the bottom wall 22 was over the35 mm. frame. The hopper 14 was then pivoted through a angle so that the developer cascaded over the electrostatic image and into the lower portion 28-ofthe apparatus. The housing 4 was then pivoted so that the developer flowed into corner 32 of the apparatus, While the film strip was simultaneously advanced to the next frame. The hopper was then returned to its original position in the apparatus -by rotation about pivot 16. The housing 4 was pivoted back so that the apparatus was 'returned'to its original position where the developer refilled the hopper 14 and the apparatus was ready to develop the next image. In this example, a single pass of developer was adequate to produce a high-density record.

While the present invention has been described with reference to the preferred embodiments thereof, it is not intended to be limitedthereto but is of the scope of the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 7

1. An apparatus for applying developer material to a rectangular area of an electrographic sheet positioned at an angle to the horizontal comprising a substantially enclosed housing for containing developer material,

said housing having a bottom wall provided with a rectangular opening centrally located therein,

the edges of said opening being in a plane and being adapted to contact and define said area, a first edge and an upper portion of said bottom wall being higher than a second edge and a lower portion of said bottom wall when said edges are in contact with said area,

said housing having an end wall extending upwardly from said lower portion and having an upper-end portion remote from said lower portion,

a hopper pivotably mounted within said housing about an axis parallel to and adjacent said first edge for rotation from a'first position, in which said hopperfits into said lowerportion for containing developer material, to a second position above said upper portion whereby developer material flows out of said hopper, into said upper portion, across said opening and into said lower portion, from whence the developer material may be moved into said upper-end portion by rotation of said housing, and

said hopper having a top end which contacts said end wall when in said first position whereby any developer material in said upper-end portion will flow back into said hopper.

2. An apparatus for applying developer material to a rectangular area of an electrographic sheet positioned at an angle to the horizontal comprising a substantially'enclosed housing for containing developer material,

said housing having a bottom wall provided with edges defining a rectangular opening centrally located therein,

said edges of said opening being in a plane and being adapted to contact said sheet and define said area,

a first edge of said opening and an upper portion of said bottom wall being higher than .a second edge of said opening, and a lower portion of said bottom wall when said edges are in contact with said area,

said housing having an end wall-extending upwardly from said lower portion of said bottom wall and having an upper-end portion remote from lower portion,

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support means for said housing and for said electrographic sheet when so positioned,

means near said lower portion pivotally mounting said housing said support means, for rotation about an axis parallel to said plane from a first position in which said edges are adapted to contact said area to a second position in which said end wall slopes downwardly from said axis,

a hopper pivotably mounted within said housing for rotation about axis parallel to and adjacent said first edge from a first location in which said hopper fits into said lower portion for containing developer material to a second location above said uppe portion for cascading developer material across said opening and into said lower portion, from whence the developer material may be moved into said upper-end portion by l ion of said housing about the first-mentioned pivotably mounting means, and

said hopper h ig a top end which contacts said end wall when in said first location whereby any developer material said uppenencl portion flows back into said hopper v hen said hopper is in said first location and said housing is rotated from said second position to said first position.

3. An apparatus for applying developer material to a rectangular area of an electrographic sheet comprising means for supporting said sheet with said area at an angle to the horizontal,

a substantially enclosed housing for containing developer material,

said housing having a bottom wall provided with a rectangular opening centrally located therein,

the edges of said opening being in a plane and being adapted to contact and define said area, a first edge and upper portion of said bottom wall being higher than a second edge and a lower portion or" said bottom wall when said edges are in contact with said area,

said housing having an end wall extending upwardly from said lower portion of said bottom wall, and having an upper-end portion remote from said lower portion,

pivot means on said sheet supporting means near said lower portion pivotably supporting said housing, said housing being movable from a first position in which said edges contact said area to a second position in which said end wall is sloped downward from said pivot means so that the developer material in said upper portion fiows across said area to said lower portion when said housing is in said first position, the developer material in said lower portion moving to said upper-end portion when said housing is moved to said second position,

conveying means mounted within said housing for receiving developer material from said upper-end portion when said housing is moved from said second position to said first position and for conveying said developer material to said upper portion from said lower portion when said housing is in said first position.

4. The apparatus according to claim 3 in which said conveying means is a hopper pivotably mounted within said housing about an axis parallel to and adjacent said first edge for rotation from a first location, in which it fits into said lover portion and abuts against said end wall for receiving developer material from said upper-end portion when said housing is rotated from said second position to said first position, to a second location above said upper portion from whence developer material fiows across said area and into said lower portion.

5. An apparatus for applying developer material to an area of an electrographic sheet positioned at an angle to the horizontal comprising a substantially enclosed housing for containing developer material,

= g centrally located therein,

the edges of said opening being in a plane and being adapted contact and define said area, a first edge and an upper portion of said bottom wall being higher than a second edge and a lower portion of said bottom wall when said edges are in contact with said area,

said housing having an end wall extending upwardly from said lower portion and having an upper-end potion remote from said lower portion,

hopper pivotably mounted within said housing about an axis parallel to and adjacent said first edge for rotation from a first position, in which said hopper fits into said lower portion for containing developer material, to a second position above said upper portion whereby developer material flows out of said hopper, into said upper portion, across said opening and into said lower portion, from whence the devel oper material may be moved into said upper-end portion by rotation of said housing, and

said hopper having a top end which contacts said end wall when in said first position whereby any developer material in said upper-end portion will flow back into said hopper.

6. An apparatus for applying developer material to an electrostatic image-bearing area on an electrographic sheet positioned at an angle to the horizontal comprising a substantially enclosed housing for containing developer material,

said housing having a bottom wall provided with edges defining an opening centrally located therein said edges of said opening being in a plane and being adapted to contact said sheet and define said area,

a first edge of said opening and an upper portion of said bottom wall being higher than a second edge of said opening, and a lower portion of said bottom wall when said edges are in contact with said area,

said housing having an end wall extending upwardly from said lower portion of said bottom wall and having an upper-end portion remote from lower portion,

support means for said housing and for said electrographic sheet when so positioned,

means near said lower portion pivotably mounting said housing on said support means, for rotation about an axis parallel to said plane from a first position in which said edges are adapted to contact said area to a second position in which said end wall slopes downwardly from said axis,

a hopper pivotably mounted within said housing for rotation about an axis parallel to and adjacent said first edge from a first location in which said hopper fits into said lower portion for containing developer material to a second location above said upper portion for cascading developer material across said opening and into said lower portion, from whence the developer material may be moved into said upper-end portion by rotation of said housing about the first-mentioned pivotably mounting means, and

said hopper having a top end which contacts said end wall when in said first location whereby any developer material in said upper-end portion flows back into said hopper when said hopper is in said first location and said housing is rotated from said second position to said first position.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN APPARATUS FOR APPLYING DEVELOPER MATERIAL TO A RECTANGULAR AREA OF AN ELECTROGRAPHIC SHEET POSITIONED AT AN ANGLE TO THE HORIZONTAL COMPRISING A SUBSTANTIALLY ENCLOSED HOUSING FOR CONTAINING DEVELOPER MATERIAL, SAID HOUSING HAVING A BOTTOM WALL PROVIDED A RECTAGULAR OPENING CENTRALLY LOCATED THEREIN, THE EDGES OF SAID OPENING BEING IN A PLANE AND BEING ADAPTED TO CONTACT AND DEFINE SAID AREA, A FIRST EDGE AND AN UPPER PORTION OF SAID BOTTOM WALL BEING HIGHER THAN A SECOND EDGE AND A LOWER PORTION OF SAID BOTTOM WALL WHEN SAID EDGES ARE IN CONTACT WITH SAID AREA, SAID HOUSING HAVING AN END WALL EXTENDING UPWARDLY FROM SAID LOWER PORTION AND HAVING AN UPPER-END PROTION REMOTE FROM SAID LOWER PORTION, A HOPPER PIVOTICALLY MOUNTED WITHIN SAID HOUSING ABOUT AN AXIS PARALLEL TO AND ADJACENT SAID FIRST EDGE FOR ROTATION FROM A FIRST POSITION, IN WHICH SAID HOPPER FITS INTO SAID LOWER PORTION FOR CONTAINING DEVELOPER MATERIAL, TO A SECOND POSTION ABOVE SAID UPPER PORTION WHEREBY DEVELOPER MATERIAL FLOWS OUT OF SAID HOPPER, INTO SAID HOPPER PORTION, ACROSS SAID OPENING AND INTO SAID LOWER PORTION, FROM WHENCE THE DEVELOPER MATERIAL MAY BE MOVED INTO SAID UPPER-END PORTION BY ROTATION OF SAID HOUSING, AND SAID HOPPER HAVING A TOP END WHICH CONTACTS SAID END WALL WHEN IN SAID FIRST POSITION WHEREBY ANY DEVELOPER MATERIAL IN SAID UPPER-END PORTION WILL FLOW BACK INTO SAID HOPPER. 